Disturbing MSN Messenger on the loose

Hi, I'm experiencing some anomalities with my MSN Messenger. (On Windows XP) When I start the program there is immediately massive activity on my line. The stream of data goes both out and in. After a little while the Messenger window comes up and all is seemingly normal, but the unwanted stream of data continues. I blocked Messenger in the firewall and did several scans of the computer using updated Norton System Works, AVG Anti-Spyware/virus 7.5, Registry Mechanic and Lavasoft ad-aware. Still no remedy. Then uninstalled Messenger and downloaded latest version and did a reinnstall. Again, the problem persists. Anyone know what it can be? Your help is much appreciated.

Thanks Tommy Indeed a lot of ports. I am no expert so find it difficult to identify exactly which ports let the data out. In the firewall program Messenger comes up 7 times. When I allow it to go through the wall, one of these instances diappears and comes back. This last entry is on for about two seconds, then goes away and comes back. Each time the port number is different..